How to setup an Exchange 2010 CAS Array to load balance MAPI

How to setup an Exchange 2010 CAS Array to load balance MAPI

Since Exchange 2010 CAS servers now handle all internal and external client traffic to Exchange mailbox servers including Outlook MAPI traffic, the need for a highly available CAS array is critical to your design.

So how do you load balance MAPI traffic? I found a some useful bits of information to help out:

The new-casarray site parameter is based on Active Directory site. Therefore, if you wanted everything in a single CAS array you would need an AD site that spanned two locations or you would need a unique CAS array residing in each site. It is currently recommended to maintain two separate AD sites.

When a failover to the alternate datacenter occurs, the database would need to be associated with the CAS array associated with the alternate AD site.

For load balancers, you can leverage Microsoft's software based NLB (Part of Windows Server) or you could leverage any hardware based load balancer. Some HW load balancers provide geo-failover capabilities which will provide an easier failover to an alternate CAS array.

Anand N

25 Dec 2009 7:37 PM

I did not get the command to work as you have it:

Set-MailboxDatabase DB1 -RpcClientAccessServer “outlook.school.edu”

I had to use a format as

Set-MailboxDatabase DB1 -RpcClientAccessServer “School Cas Array”

Kenan DUZDAS

4 Jan 2010 9:26 AM

Hi everyone,

I have a problem,I have two CAS server and two Mailbox exchange,I have configured CAS-NLB but i haven't connectted to database,When I used that command "Set-MailboxDatabase DB1 -RpcClientAccessServer “outlook.school.edu” I got the following warning " WARNING: The command completed successfully but no settings of 'Mailbox Database 0774792730' have been modified." i didn't configure DAG on mailbox exchange, is this important? or what is the problem?

This would imply TWO CAS arrays since it is a one to one mapping. Manual DNS switching would be required for CAS failover if you have TWO DAGs amongst the two sites. If you have stretched DAG across the two sites you would have to re-associate the users to the CAS Array in Site 2 using the Set-Mailboxdatabase -RPCClientCASserver cmdlet above to manually change the CAS Array in Site 2.

You want a unique FQDN for your CAS Array since it is used for load balancing all CAS traffic amongst your CAS servers. You can use whatever name you want of course for your CAS array. It certainly could replace your OWA FQDN with mail.x.edu and then specific subdirs such as /owa routes to OWA and MAPI RPC routes Outlook traffic, etc.